The data to be transmitted or stored to a storage medium having errors so vulnerable, like the noise that occurs during the transmission or there is a hardware error. To ensure the integrity of the data to be transmitted or stored, the CRC can be used. CRC works in a simple, ie, by using mathematical calculations on a number called a checksum, which is based on the total bits to be transmitted or who want to be saved.
In the transmission network, especially in the network based on Ethernet technology, the checksum will be calculated on each frame shall be transmitted and added to the frame such as the information in the header or trailer. Recipients will recalculate the frame if the frame that he received absolutely no damage, by comparing the calculated value of the frame with the frame value contained in the header frame. If two values are different, then the frame has been changed and should be sent back.
CRC is designed to ensure data integrity against degradation due to random noise or other sources (damage to the media and others). CRC does not guarantee data integrity from the threat of modification to treat any suspicious by hackers, because the attackers can recalculate the checksum value checksum and replace the old with the new one to fool recipients.